Blind rivets, that is to say rivets which can be set into a workpiece with access only to one side of the workpiece, have been suggested in many different configurations and for many different purposes. They can conveniently be divided into two classes, those which have an expendable mandrel assembled with a rivet body and those which are set with a mandrel which is part of a tool.
It is sometimes required, for example in the manufacture of automobiles, to secure a small tube to a workpiece for example to provide a drain hole. Such a small tube may conveniently be provided by a blind rivet but, because it is required to have a passage right through the rivet, blind rivets of the first class, that is to say those with an expendable mandrel, are not satisfactory as a head portion of the mandrel is often left in the rivet after setting, thus obstructing the passage through the rivet.
It is therefore desirable to provide a blind rivet which is set with a mandrel which is part of a tool which may conveniently be set in a workpiece to provide a small tube.
A rivet is described in UK 584286 which is adapted to be set by a mandrel of a setting tool comprising a rivet body having a tubular wall surrounding an axial bore which extends from a tail end portion to a head end portion of the rivet, a head flange at the head end portion of the rivet extending outwardly from the rivet body, abutment means at the tail end portion of the rivet and comprising diametrically opposed lugs extending generally radially inwards of the wall of the rivet body. When it is desired to set such a rivet, a mandrel having a cylindrical stem and outwardly extending setting lugs complementary in shape to the lugs of the rivet is passed through the axial bore of the rivet from the head flange outwardly of the tail end portion, the lugs of the mandrel passing between the lugs of the rivet. The mandrel is then rotated through a small angle to bring the lugs of the mandrel into line with the lugs of the rivet, and relative axial movement is then caused between the rivet and the mandrel to cause the rivet to be set, and the mandrel is then again rotated so that its lugs are in line with the gaps between the lugs of the rivet and the mandrel is withdrawn.
This procedure suffers from a serious disadvantage. By the nature of blind riveting the tail end portion of a rivet being set, and the lugs on the mandrel being used to set it, are not visible. For a reliable setting of the rivet it is an essential that the lugs on the mandrel be properly aligned with the lugs on the rivet, and there is no way that an operator can check that this is the case.
It is one of the objects of the present invention to provide a blind rivet which can reliably be set into a workpiece to provide a small tube fixed in the workpiece.